fix: harden account rotation and active download recovery

Apply account enablement changes optimistically and persist rapid toggles sequentially without losing clicks.

Refresh Mega-Debrid API and Web account pools during active downloads, isolate per-account cancellation budgets, rotate within the same conversion attempt, and keep pause, stop, resume, reset, and no-account gates consistent.

Use the native Electron clipboard under Remote Desktop and make support bundle export bounded, redacted, responsive, guarded, visible, and atomic.

Add end-to-end regressions for live account switching, persisted partial recovery, support export, native copy, availability preservation, and the 500 ms telemetry cadence.

tests/downloads-view.test.tsx

@@ -708,7 +708,7 @@ describe("downloads view", () => {
     expect(renderToStaticMarkup(toolbar)).not.toContain("Reconnect");
   });
 
-  it("blocks resume without a usable account and keeps pause independent from unrelated action busy state", () => {
+  it("blocks resume without a usable account and keeps lifecycle controls independent from unrelated action busy state", () => {
     const pausedToolbar = DownloadsToolbar({
       actions: createActions(),
       model: withRuntime(createInput(), { paused: true, canStart: false, canPause: true })
@@ -721,6 +721,7 @@ describe("downloads view", () => {
     expect(findButton(pausedToolbar, "Start").props.disabled).toBe(true);
     expect(findButton(pausedToolbar, "Pause").props.disabled).toBe(true);
     expect(findButton(busyToolbar, "Pause").props.disabled).toBe(false);
+    expect(findButton(busyToolbar, "Stop").props.disabled).toBe(false);
   });
 
   it("enables package movement only for a visible selected package row", () => {